Nowadays inkjet printing systems are used in a wide array of apparatuses in a wide array of applications such as fax, colour photo printing, industrial applications etc. In these printing systems inks, possibly of various colours, is ejected out of an array of nozzles located in a print head to the receiving material.
A long known problem in inkjet printers is that the nozzles through which the ink is projected to the receiving material are blocked by clogging of ink inside the nozzles and on the print head. This renders certain nozzles inoperable and results in a defective print of deteriorated print quality.
To improve the clarity and contrast of the printed image, recent research has been focused to improvement of the used inks. To provide quicker, more waterfast printing with darker blacks and more vivid colours, pigment based inks have been developed. These pigment-based inks have a higher solid content than the earlier dye-based inks. Both types of ink dry quickly, which allows inkjet printing mechanisms to forms high quality images.
In some industrial applications, such as making of printing plates using ink-jet processes, inks having special characteristics causing specific problems. e.g. UV curable inks exist to allow rapid hardening of inks after printing.
The combination of small nozzles and quick drying ink leaves the print heads susceptible to clogging, not only from dried ink and minute dust particles or paper fibres, but also from the solids within the new ink themselves.
It is known to counteract or correct the problem of clogging by protecting and cleaning the print head by various methods.                Wiping: Before an during printing the inkjet print head is wiped clean by using an elastomeric wiper, removing ink residue, paper dust and other impurities.        Capping: during non-operational periods the print head can sealed off from contaminants by a sealing enclosure. This also prevents the drying of the ink. The capping unit usually consists of a rubber seal placed around the nozzle array.        Spitting: by periodically firing a number of drops of ink through each nozzle into a waste ink receiver, commonly called a spittoon, clogs are cleared from the nozzles. This can be concentrated to nozzles which are not used for a certain time but usually all the nozzles are actuated during spitting.        Vacuum assisted purging: During a special operation in order to clear partially or fully blocked nozzles a printing is actuated while on the outside of the nozzles a vacuum is applied. This helps clearing and cleansing the nozzles. The purging is normally performed when the print head is in the capping unit as this unit can provide a good seal around the nozzle array for building the vacuum.        
Also other methods exist for cleaning an inkjet print head which may include applying solvents as in EP-A-1 018 430,
These features designed to clean and to protect a print head, are commonly concentrated in a service station which is mounted within the plotter chassis, whereby the print head can be moved over the station for maintenance. An example of such a service station can be found in U.S. Pat. No. 6,193,353 combining wiping, capping, spitting and, purging functions.
State of the art printers have relatively small printheads having only a limited number of nozzles
The wiper systems of these printheads have also relative small dimensions. E.g. a typical wiper has a length of only 10 mm. Nowadays however industrial, large volume, ink jet printers have been developed wherein larger printheads are used.
Printing speeds, ink consumption are much larger than the state of the art home and office printing machines.
The dimension of such an industrial printhead may well be up to 80 mm. In order to clean these large printheads, large size wipers are needed.
Wiper assemblies made according to the state of the art show several deficiencies when trying to use the same manufacturing methods for larger wipers.                It is relatively easy to ensure a good and even mounting for a short wiper. Small variations in mounting over the length of the wiper will not lead to problems as the overall variation is limited due to the small dimension of the wiper.         When using relatively large wiper the variations may be greater due to the length.         A very small variation of in the mounting height for a wiper poses no problem, but variations of 0.2 mm in mounting height have an adverse effect on the cleaning of the nozzle plate and thus also on the printing quality. Achieving this tolerance for a 10 mm wide wiper may pose no problem, but such an accurate mounting precision for a wiper of about 70 mm is not easy to achieve. Uneven cleaning and printing is likely to occur using state of the art wipers.        Uneven mounting can be in height but also the clamping forces of the wiper holder may vary which influences the slip of the sides of the wiper relatively to the wiper holder. Even a difference in surface finish of the wiper holder can cause variations.        
Better mounting method need to be used in mounting the large wipers used in industrial inkjet printing apparatuses.
Another problem is that fabrication of unitary wipers, used in several state of the art printers, containing two or more blades with a length (e.g. 80 mm) for industrial applications is not easy and thus expensive.                consistent properties of the two or more wipers over the large wiper length is not easy to obtain. Variation on both wiper blades may occur and to obtain constant properties, both wipers need to have constant properties.        The unitary wiper can not be partially replaced, e.g. when the front wiper blade is worn out before the other wiper blades.        Both blades have the same chemical composition. Making a unitary wiper with wiper blades having a different composition or internal structure is difficult and expensive. It is desirable to have the possibility to give front and rear wipers another composition and structure        Due to the unitary fabrication the bending of one wiper blade may influence the position of adjacent wipers via the common base.        As in industrial printing apparatuses it is possible to use different types of ink, it is desirable to be able to exchange the wipers, and printheads, easily to allow quick switchover.        
Another problem associated with wipers is that during the process of wiping ink adhered to the wiper blade can be flung away when the wiper clears the printhead. The wiper is full of ink as wiping of the nozzle plate is just finished and the recoiling wiper blades flings ink around contaminating the interior of the printer.
Although this problem is already known in small scale printers of office and home applications, it is larger in industrial printers as the wipers are also considerably larger in size. Measurements have to be taken to avoid this type of contamination.
Due to the large build-up of eventually dried ink on the wiper, the wiper needs to be cleaned by scraping it along a scraper. Frequent scraping of the wiper causes premature wear resulting in lower wiping efficiency and frequent need to replace the wipers which requires expensive intervention of a technician.
Another problem is that dried ink adhered to the printhead.